This invention relates to a novel primary intermediate for use in hair coloring compositions comprising one or more oxidative hair coloring agents in combination with one or more oxidizing agents. The invention also relates to hair coloring compositions of this novel primary intermediate and to coloring or dyeing of hair using compositions containing this primary intermediate.
Coloration of hair is a procedure practiced from antiquity employing a variety of means. In modern times, the most extensively used method employed to color hair is to color hair by an oxidative dyeing process employing hair coloring systems utilizing one or more oxidative hair coloring agents in combination with one or more oxidizing agents.
Most commonly a peroxy oxidizing agent is used in combination with one or more oxidative hair coloring agents, generally small molecules capable of diffusing into hair and comprising one or more primary intermediates and one or more couplers. In this procedure, a peroxide material, such as hydrogen peroxide, is employed to activate the small molecules of primary intermediates so that they react with couplers to form larger sized compounds in the hair shaft to color the hair in a variety of shades and colors.
A wide variety of primary intermediates and couplers have been employed in such oxidative hair coloring systems and compositions. Among the primary intermediates employed there may be mentioned p-phenylenediamine, p-toluenediamine, p-aminophenol, 4-amino-3-methylphenol, and as couplers there may be mentioned resorcinol, 2-methylresorcinol, 3-aminophenol, and 5-amino-2-methylphenol. A majority of the shades have been produced with dyes based on p-phenylenediamine.
However, U.S. Pat. Nos. 5,599,353 and 5,538,516 describe that continued use of p-phenylenediamine is being questioned for toxicological reasons, mainly due to a strong sensitization potential. British patent publication GB 2,239,265A describes that some individuals (para-allergic persons) are being sensitized to p-phenylenediamine and its derivatives. In replacing p-phenylenediamine, EP 400,331 B1 and GB 2,239,205A describe the use of 2-(2-hydroxyethyl)-p-phenylenediamine. However, 2-(2-hydroxyethyl)-p-phenylenediamine is not sufficiently stable. The free base oxidizes and loses its dyeing ability over extended storage, even if stored in dark and sealed containers. Therefore, this compound is employed in its salt form. Additionally, the synthesis of 2-(2-hydroxyethyl)-p-phenylenediamine is relatively complex. Thus, the complexity of the synthesis procedure required, the necessity to convert the primary intermediate to its salt form, and its use in the salt form to formulate dyeing compositions adds unwanted expense and complexity to the production of hair coloring compositions. In the absence of the use of the compound in its salt form, reliable dyeing cannot be obtained if the free base form is utilized after extended periods of storage thereof.
Pyrimidine derivatives, such as tetraaminopyrimidine, have also been suggested as alternatives to p-phenylenediamine (see US Re. 30,199 [U.S. Pat. No. 4,003,699]). However, GB 2,239,265A points out that although the use of pyrimidine derivatives as developers has reduced toxicological problems, the pyrimidine derivatives are not completely satisfactory with respect to coloring performance.
U.S. Pat. No. 5,421,833 discloses hair dye compositions asserted to be without sensitizing potential. The dye compositions are disclosed to possess improved dyeing properties for all shades. The compositions comprise only 2-(2-hydroxyethyl)amino-5-aminotoluene in combination with the usual coupling agents (with the exclusion of 1-methoxy-2,4-diaminobenzene and 1-ethoxy-2,4-diaminobenzene).
It is therefore an object of the present invention to provide a more suitable alternative to p-phenylenediamine as a primary intermediate in hair coloring compositions and systems.
It is a further object of this invention to provide a more suitable alternative to p-phenylenediamine as a primary intermediate that can be easily prepared and is more stable in the free base form than the intermediate 2-(2-hydroxyethyl)-p-phenylenediamine suggested in the aforementioned EP 400,330 B1 and GB 2,239,265A publications.
It has been discovered that the novel compound 1-(2,5-diaminophenyl)ethanol of the formula 1: 
is easily prepared and is unexpectedly significantly more stable in its free base form than 2-(2-hydroxyethyl)-p-phenylenediamine and, therefore, provides a significantly improved primary intermediate for oxidative hair coloring compositions and systems. This novel primary intermediate is also much less susceptible to cause sensitization than p-phenylenediamine, i.e., it has a weaker sensitization potential.
This invention therefore provides this novel primary intermediate, a process for its production, and hair coloring compositions and systems employing this novel primary intermediate.
Whereas current technology generally requires p-phenylenediamine or p-toluenediamine for producing red and black shades (see U.S. Pat. No. 5,538,516), the present invention enables one skilled in the art to formulate a natural black shade and dark red shade through the use of 1-(2,5-diaminephenyl)ethanol without relying on p-phenylenediamine (see Tables 1 and 2). It is also advantageous that the shades obtained through use of 1-(2,5-diaminophenyl)ethanol have good wash, weather, and light fastness.
A process for the preparation of the 1-(2,5-diaminophenyl)ethanol is new and commercially feasible. The synthesis of 1-(2,5-diaminophenyl)ethanol can be accomplished by reduction of 1-(2-amino-5-nitrophenyl)ethanone to 1-(2-amino-5-nitrophenyl)ethanol and then hydrogenating the 1-(2-amino-5-nitrophenyl)ethanol to convert the nitro group to an amino group whereby 1-(2,5-diaminophenyl)ethanol is produced.
1-(2,5-Diaminophenyl)ethanol has excellent solubility in water. Water solubility is important because hair dye formulations employed for hair coloring are in large part water. Moreover, the free base evidences excellent long term storage stability.
The novel 1-(2,5-diaminophenyl)ethanol primary intermediate of this invention can be prepared from the known compound 1-(2-aminophenyl)ethanone as indicated previously or by a synthesis process starting from the known compound 1-(2-aminophenyl)ethanone 2 according to the following reaction scheme: 
To 1-(2-amino-phenyl)-ethanone 2 (90.37 g, 0.67 moles) was added acetic anhydride (68.25 g, 0.67 moles) and stirred for 2 h at 4xc2x0 C. The reaction mixture was poured into crushed ice and the precipitate was filtered, washed with ice water, and air-dried to afford N-(2-acetyl-phenyl)-acetamide 3 (104.70 g, 88% yield). 1HNMR (400 MHz, DMSO-d6) xcex42.10 (s, 3H), 2.60 (s, 3H), 7.17-7.21 (m, 1H), 7.55-7.59 (m, 1H), 7.95 (d, 1H, J=8.0 Hz), 8.26 (d, 1H, J=8.0 Hz), 11.16 (s 1H); MS m/z 17 (M+).
The amide 3 (104.70, 0.59 moles) was added portion-wise over 0.5 h to a mixture of sulfuric acid (250 mL) and fuming nitric acid (250 mL) at 4xc2x0 C. and stirred for another 1.5 h. The reaction mixture was poured into crushed ice and the precipitate filtered, washed with water, and air-dried to afford N-(2-acetyl-4-nitro-phenyl)-acetamide 4 (85.56 g, 65% yield). 1HNMR (400 MHz, DMSO-d6) xcex42.18 (s, 3H), 2.70 (s, 3H), 8.41-8.47 (m, 2H), 8.70 (dd, 1H, J=2.6, 10.4 Hz), 11.42 (s, 1H); MS m/z 222 (M+).
A mixture of 4 (85.56 g, 0.39 moles) and 6 N HCl (600 mL) was stirred for 2 h at 80xc2x0 C. The suspension was filtered, washed with water, and air-dried to afford 1-(2-amino-5-nitro-phenyl)ethanone 5 (54.95 g, 79% yield). 1HNMR(400 MHz, DMSO-d6) xcex42.61 (s, 3H), 6.86 (d, 1H, J=9.4 Hz), 8.07 (dd, 1H, J=2.6, 9.4 Hz), 8.61 (d, 1H, J=2.6), 8.08-8.61 (bs, 2H); MS m/z 180 (M+).
To a stirred suspension of 5 (27.02 g, 150 mmole) in methanol (150 mL) at 4xc2x0 C. was added sodium borohydride (5.67 g, 150 mmole) over a period of 0.25 h. After the addition was complete, the solution was warmed to room temperature and stirred for 0.25 h. The methanol was evaporated under vacuum. Water (150 mL) was added to the residue and the precipitate was filtered, washed with cold water, and air dried to afford 1-(2-amino-5-nitro-phenyl)-ethanol 6 (27.0 g, 99% yield). 1HNMR (400 MHz, DMSO-d6) xcex41.27 (d, 3H, J=6.3), 4.77-4.82 (m, 1H), 5.36 (d, 1H, J=4.3 Hz), 6.50 (s, 2H), 6.63 (d, 1H, J=9.0 Hz), 7.85 (dd, 1H, J=2.8, 9.0 Hz), 8.07 (d, 1H, J=2.6); MS m/z 182 (M+).
Catalytic hydrogenation of 6 (27.0 g, 150 mmole) under 60 psi hydrogen pressure with 10% Pd/C (2.7 g) in anhydrous MeOH (150 mL)/ethyl acetate (150 mL) was completed in 2.5 h. The catalyst was removed by filtration over Celite. The filtrate was evaporated under vacuum to afford 1-(2,5-diamino-phenyl)-ethanol 1 (22.83 g, 100 % yield). Mp 124xc2x0 C.; 1HNMR (400 MHz, DMSO-d6) xcex41.26 (d, 3H, J=6.4 Hz), 4.15 (d, 4H, J=10.7 Hz), 4.61-4.65 (m, 1H), 4.94 (d, 1H, J=3.6 Hz), 6.24 (dd, 1H, J=2.5, 8.2 Hz), 6.36 (d, 1H, J=8.2 Hz), 6.45 (d, 1H, J=2.5 Hz); MS m/z 152 (M+); Anal. Calcd. for C8H12N2O: C, 63.13. H, 7.95. N, 18.41.O, 10.51. Found: C, 62.83. H, 7.90. N, 18.46. O, 10.17.
Hair coloring compositions of this invention can contain 1-(2,5-diaminophenyl)ethanol as the sole primary intermediate or can also contain other primary intermediates and couplers.
It should be noted that for certain dark shades, including dark brown and black shades, it is desirable to include a meta diamine as one of the couplers. Suitable meta diamines include m-phenylenediamine, 2,4-diaminophenoxyethanol and 4,6-bis(2-hydroxyethoxy)-m-phenylenediamine. For certain dark shades of red coloring, it is desirable to include 2-methyl-5-aminophenol as a coupler.